In electric power conversion devices, it is common practice to employ a full-wave diode-bridge rectifier circuit as a converter circuit to convert AC power into DC power, which is then input into an inverter circuit. Oftentimes, a large smoothing capacitor, such as an electrolytic capacitor, is installed between the converter circuit and the inverter circuit in order to supply a DC with a weak pulse to the inverter circuit.
In the above converter circuit, a rectifier diode conducts current only in a period when an absolute value of an input voltage is higher than a voltage of the smoothing capacitor. Therefore, the waveform of the input current of the converter circuit develops spikes, which negatively affects the power factor and results in the current including a harmonic component.
Moreover, an input reactor is employed in electric power conversion devices. However, since a high inductance is required to obtain an appropriate power factor and appropriate harmonics of a power source, components of the electric power conversion device need to be increased in volume and weight.
As a countermeasure, it has been attempted to improve the power factor and to reduce the harmonics in an electric power conversion device by boosting an AC, which is input into a diode bridge circuit (see, e.g., Patent Document 1). In Patent Document 1, a diode bridge circuit, which is supplied with an AC via a reactor, is provided. Apart from that, a power factor correction circuit is provided between all phase output terminals of the reactor and a negative terminal of the diode bridge circuit. The power factor correction circuit includes a switching element, which switches the reactor between energy storage and energy discharge. In a power factor correction circuit employing such a boost circuit, a small reactor can be employed since an inductance of the reactor can be kept relatively low.
In a different example, a conduction width of a diode bridge circuit is widened and a power factor is corrected by providing a DC link section, which is located between a converter circuit and an inverter circuit, with a capacitor of a relatively small capacitance (see, e.g., Patent Document 2).